Reversible propeller



March 23, 1965 H. K. MONROE REVERSIBLE PROPELLER Filed Feb. 27, 1965 INVENTOR. HOW/[1? KNOW/F06 United States Patent 3,174,681 REVERSBLE PRUPELLER Homer K. Monroe, Piqua, Ohio, assignor to Aerovent Fan Company, Inc, Piqua, Ohio, a corporation of Ohio Filed Feb. 27, 1963, Ser. No. 261,318 3 Claims. (Cl. 230-134) This invention relates to reversible propeller fans and particularly to a generally new blade construction therefor.

The blade section of a reversible propeller may have the same configuration on the face as on the back thereof, these terms having regard to the direction of air flow through the propeller and being interchangeably applied to the opposing surfaces of a reversible propeller blade. Within this general concept, however, a blade is subject to varying structural and design approaches.

The object of the invention is to simplify the construction as well as the means and mode of operation of reversible propeller fans, whereby such fans may not only be economically manufactured, but will be more efficient and satisfactory in use, adaptable to a wide variety of application, and be unlikely to get out of order.

A further object of this invention is to accomplish good and uniform fan performance, under high efficiency conditions, irrespective of the direction of rotation.

Another object of the invention is to adapt a propeller as described more readily to manufacture from ordinary sheet metal stock, it being an attendant object in this connection to give the blade a configuration imparting stiffness and permitting use of relatively thin sheet stock.

A further object of the invention is to provide a blade construction lending itself to inexpensive and simplified making by any of the conventional methods of manufacture, for example by casting or by stamping and forming sheet metal.

Still another object of the invention is to provide a blade section of a reversible propeller fan having a high level of performance by reason of a unique construction characterized in part by substantially uniform width and thickness from hub to tip.

A further object of the invention is to provide a reversible propeller fan possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

FIG. 1 is a diagram of a propeller fan mounted in a duct, showing the utility of a propeller fan in accordance with the illustrated embodiment of the invention;

FIG. 2 is a fragmentary top-plan view of a part of a propeller assembly comprising a hub and a blade section projecting outwardly thereof;

FIG. 3 is a side view of the device of FIG. 2, enlarged relatively thereto and showing the hub in cross-section;

FIGS. 4 through 8 are views in cross-section taken substantially along correspondingly indicated lines in FIG. 3 and arranged to depict by comparison with one another a progressively changing blade angularity.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawings, the present blade structure has, as noted, particular application to propeller fans. It

3,17%,fi8l Patented Mar. 23, 1955 may thus find embodiment in a device as indicated in FIG. 1. In the illustrated instance a duct 10 has installed therein an assembly comprising a reversible electric motor 11 and a propeller fan 12., the latter being mounted on' and rotated by a shaft 13 extending directly from the motor 11. In the operation of the device, energizing of the motor 11 drives the propeller fan 12 alternatively in what may be considered forward and reverse directions with the result that air, products of combustion or other gaseous fluids are moved throught the duct 10 in a direction determined by the direction of rotation of the fan. The propeller fan member 12 is comprised of a central hub 14 from which project in radial fashion a number of blade sections 15.

Referring to propeller fan illustratively shown in FIG. 1, the invention is more particularly concerned, with an improved blade section yielding the advantageous results heretofore noted. According to a feature of the invention the propeller fan blades may be constructed of conventional materials and by conventional means. In the illustrated instance the hub and blade section are made of of a suitable metal, such as aluminum. The hub 15 comprises a central bushing portion 16 adapted to receive and to be connected to a rotating shaft. An annulus 1'7 surrounds bushing portion 16 and joins it integrally to a radially spaced flange 18 marking the periphery of the hub 14. The blade sections project radially from the hub 14 and are secured thereto as by being formed integrally with the hub or in an assembly process by which the blades are separately formed and attached at What may be their inner ends to the flange 18.

The blade section 15 is a one-piece elongate member made relatively broad and flat to have a generally rectangular configuration. Opposing broad surfaces H and Z] of the blade, designated for convenience the face and back thereof, merge at their one ends with the hub 14. At their opposite ends the surfaces 19 and 21 terminate in an arcuate tip 22 and at their sides in rounded edges 23 and 24. The latter join the surfaces 19 and 21 and are formed identically to one another. They perform interchangeably the function of trailing and leading edges depending upon the direction of rotation of the fan.

In cross-sectional outline the blade section 15 has an undulating, S-like shape describing an ogee curve. Thus each surface 19 and 21 is formed with side by side convex and concave portions contiguous along a line parallel to the center axis of the blade, with such surfaces being inversely arranged so that the concave portion of one surface is aligned with and complements the convex portion of the other surface. The blade is symmetrical and balanced about the described center axis, the location of which is diagrammatically indicated in FIGS. 4 through 8 at 25.

The curvature of the blade is the same from end to end thereof giving a cross-sectional outline which is the same in any transverse plane taken along the length of the blade. Likewise the thickness of the blade section does not diminish nor increase from the hub to the tip so that the blade thickness may be described as substantially uniform. Additionally, the width of the blade section is substantially uniform throughout its length or from the hub to the tip thereof. In the illustrated instance the width and thickness of the blade section are uniform and they are described herein as substantially uniform out of consideration of the fact that slight departures from such uniformity may be made without departing from the instant inventive teaching.

The blade configuration as disclosed produces an airfoil shape for identical high efficiency performance of a fan in either direction of rotation. The curvature of the blade, its uniformity of width and thickness tends to improve the performance of the propeller by comparison to other known designs and contributes, moreover, to a simplified and more economical production thereof. The shape of the blade incorporates strength and rigidity therein, allowing the blade to be made relatively thin, for example from sheet metal stock while retaining the necessary stifiness for use as a propeller. Also, the uniformity of width and thickness obviates problems inherent in the formation of parts having tapering or progressively changing dimensions. For example simplified shearing and punching tools may be'used in stamping out the blades when made of sheet metal stock as described.

Propeller blades conventionally have a built-in twist or rotational angularity predetermined to achieve the desired propulsion effect. In the illustrated instance this angle is formed progressively to decrease toward the tip of the blade within a range found to produce advantageous results, for example from approximately 31'degrees at the hub to approximately 19 degrees at a tip. However, be-

cause the present blade design provides a uniform thickness from hub to tip and because of the inherent characv teristics of the particular airfoil design, the pitch distribution is relatively unimportant. Assuming the blade to be set within a normal range of angles known to be satisfactory for propeller fans, the selected angle can be uniform from hub to tip with good results.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages. V

While in order to comply with the statute the invention has been described in language more ;or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A reversible axial flow propeller comprising a central hub and at least one elongated sheet metal blade merging with said hub, said blade having a substantially radially extending spanwise axis and said blade being defined by an ogee surface having identical portions on opposite sides of the spanwise axis, said blade being progressively twisted at a decreasing rate from approx imately 31 degrees at said hub to about 19 degrees at its tip whereby equal volumes of fluid will be propelled in either direction of rotation of said propeller.

2. The structure according to claim 1 in which said elongated sheet metal blade is of uniform thickness in cross section from where it merges with said hub to its tip..

3. The structure according to claim 1 in which the sheet metal blade has an arcuate or rounded tip at the extreme end of the blade removed from said hub.

References fitted hy the Examiner UNITED STATES PATENTS 909,246 1/ 09 Spear 170-159 1,649,057 11/27 Bunkenburg 170-159 1,653,342 12/27 Chillingworth 170-165 1,668,462 .5/28 Oswald 230-134 1,706,316 3/29 Norton et a1 230-134 2,260,169 10/41 Couch 230-134 2,532,371 12/50 Petersen 230-134 2,609,055 a 9/52 Monroe 230- 2,667,936 2/54 Clark -159 2,784,551 3/57 Karlby et a1. 230-120 FOREIGN PATENTS 4,410 5/05 France;

(2nd addition to 340,328) 11,624 11/ 80 Germany. 538,547 8/41 Great Britain.

JOSEPH H. BRANSON, 13., Primary Examiner, 

1. A REVERSIBLE AXIAL FLOW PROPELLER COMPRISING A CENTRAL HUB AND AT LEAST ONE ELONGATED SHEET METAL BLADE MERGING WITH SAID HUB, SAID BLADE HAVING A SUBSTANTIALLY RADIALLY EXTENDING SPANWISE AXIS AND SAID BLADE BEING DEFINED BY AN OGEE SURFACE HAVING IDENTICAL PORTIONS ON OPPOSITE SIDES OF THE SPANWISE AXIS, SAID BLADE BEING PROGRESSIVELY TWISTED AT A DECREASING RATE FROM APPROXIMATELY 31 DEGREES AT SAID HUB TO ABOUT 19 DEGREES AT ITS TIP WHEREBY EQUAL VOLUMES OF FLUID WILL BE PROPELLED IN EITHER DIRECTION OF ROTATION OF SAID PROPELLER. 